The Ca transport and release function of sarcoplasmic reticulum is important in the regulation of contraction relaxation cycle in skeletal muscle. We will study the regulation of gene expression leading to the synthesis of Ca tranport ATPase in sarcoplasmic reticulum membranes, both in vivo and in tissue culture. The elementary step of ATP hydrolysis will be analyzed by rapid kinetic technique in order to define the mode of involvement of phospholipids in the process. Attempts will be made to analyse the mechanism of fast Ca release from reconstituted ATPase-phospholipid vesicles and to correlate it with the Ca permeability of sarcoplasmic reticulum membranes in living muscle. BIBLIOGRAPHIC REFERENCES: A. Martonosi. Membrane Transport During Development in Animals. (A review) Biochim. Biophys. Acta, 415, 311-333 (1975). R.L. Coffey, E. Lagwinska, M. Oliver, and A. Martonosi. The Mechanism of ATP Hydrolysis by Sarcoplasmic Reticulum. Arch. Biochem. Biophys., 170, 37-48 (1975).